Process for separation of dewaxed lube oil into light and heavy products

Abstract

Methods and apparatus to separate a light lube stock product and a heavy lube stock product from heavy dewaxed lube oils are described which maintain product specifications while utilizing conventional refinery equipment. The heavy dewaxed lube oil stream is first heated, such as in a spiral heat exchanger in the top of a vacuum stripper, with the heavy lube stock fraction, and/or with hot oil. Next, the heated heavy dewaxed lube oil stream is injected into the vacuum stripper, and fuel gas is injected at the bottom of the stripper as the stripping medium. A light lube stock fraction is removed from the upper portion of the stripper, and a heavy lube stock fraction is removed from the lower portion thereof. Optionally, the gas stripping medium is removed from the top of the stripper by a vacuum pump and used to fuel a hot oil exchanger to heat the oil which in turn is employed to heat the heavy dewaxed lube oil stream.

We claim:  
     
       1. A process for separating heavy dewaxed lube oils, comprising: 
       a) heating a heavy dewaxed lube oil stream;  
       b) injecting the heated heavy dewaxed lube oil stream into a vacuum stripper at a feed point;  
       c) injecting a gas stripping medium at a lower portion of the vacuum stripper;  
       d) removing a light lube stock fraction from an upper portion of the vacuum stripper; and  
       e) removing a heavy lube stock fraction from a lower portion of the vacuum stripper.  
     
     
       2. The process of  claim 1  where the gas stripping medium is fuel gas. 
     
     
       3. The process of  claim 1  further comprising: 
       f) removing the gas stripping medium from the top of the stripper by a vacuum pump; and  
       g) using at least a portion of the removed gas stripping medium to fuel a fired heater that heats oil to heat the heavy dewaxed lube oil stream.  
     
     
       4. The process of  claim 1  further comprising: 
       h) condensing the light lube stock fraction by heating the heavy dewaxed lube oil stream in a spiral heat exchanger in the top of the vacuum stripper.  
     
     
       5. The process of  claim 1  further comprising: 
       i) heating the heavy dewaxed lube oil stream with the heavy lube stock fraction.  
     
     
       6. The process of  claim 1  further comprising: 
       j) heating the heavy dewaxed lube stock stream with hot oil.  
     
     
       7. The process of  claim 1  where the vacuum stripper is operated at a temperature of 650° F. (343° C.) or less. 
     
     
       8. The process of  claim 1  where the vacuum stripper is operated at a pressure of 10 mm Hg (1.3 kPa) or above. 
     
     
       9. The process of  claim 1  where the light lube stock fraction is removed from the vacuum stripper above the feed point. 
     
     
       10. A process for separating heavy dewaxed lube oils, comprising: 
       a) heating a heavy dewaxed lube oil stream;  
       b) injecting the heated heavy dewaxed lube oil stream into a vacuum stripper at a feed point;  
       c) injecting a gas stripping medium at a lower portion of the vacuum stripper;  
       d) operating the vacuum stripper at a temperature of 650° F. (343° C.) or less and at a pressure of 10 mm Hg (1.3 kPa) or above;  
       e) removing a light lube stock fraction from an upper portion of the vacuum stripper; and  
       f) removing a heavy lube stock fraction from a lower portion of the vacuum stripper.  
     
     
       11. The process of  claim 10  where the gas stripping medium is fuel gas. 
     
     
       12. The process of  claim 10  further comprising: 
       f) removing the gas stripping medium from the top of the stripper by a vacuum pump; and  
       g) using at least a portion of the removed gas stripping medium to fuel a fired heater that heats oil to heat the heavy dewaxed lube oil stream.  
     
     
       13. The process of  claim 10  further comprising: 
       h) condensing the light lube stock fraction by heating the heavy dewaxed lube oil stream in a spiral heat exchanger in the top of the vacuum stripper.  
     
     
       14. The process of  claim 10  further comprising: 
       i) heating the heavy dewaxed lube oil stream with the heavy lube stock fraction.  
     
     
       15. The process of  claim 10  further comprising: 
       j) heating the heavy dewaxed lube oil stream with hot oil.  
     
     
       16. The process of  claim 10  where the light lube stock fraction is removed from the vacuum stripper above the feed point. 
     
     
       17. The process of  claim 10  where the heavy dewaxed lube oil stream is a dewaxed bright stock stream, the light lube stock fraction is a light bright stock fraction, and the heavy lube stock fraction is a heavy bright stock fraction. 
     
     
       18. A process for separating heavy dewaxed lube oils, comprising: 
       a) heating a dewaxed bright stock stream:  
       1) in a spiral heat exchanger in the top of the vacuum stripper;  
       2) with a heavy bright stock fraction; and  
       3) with hot oil;  
       b) injecting the heated dewaxed bright stock stream into a vacuum stripper at a feed point;  
       c) injecting fuel gas at a lower portion of the stripper as the stripping medium;  
       d) operating the vacuum stripper operated at a temperature of 650° F. (343° C.) or less and at a pressure of 10 mm Hg (1.3 kPa) or above;  
       e) removing a light bright stock fraction from an upper portion of the vacuum stripper above the feed point;  
       f) removing a heavy bright stock fraction from a lower portion of the vacuum stripper;  
       g) removing the gas stripping medium from the top of the vacuum stripper by a vacuum pump;  
       h) using at least a portion of the removed gas stripping medium to fuel a fired heater that heats the oil to heat the dewaxed bright stock stream; and  
       i) condensing the light bright stock fraction by heating the dewaxed bright stock stream with the light bright stock fraction in the spiral heat exchanger.